1. Field of the Invention
The present invention relates generally to photosensitive polymers and photoresists and more particularly, to a photosensitive polymer, a dissolution inhibitor, and a chemically-amplified photoresist composition containing the same.
2. Description of the Related Art
Since current semiconductor chips are highly integrated, it is generally essential to form fine patterns in photolithography. In particular, a device of 1Gbit or more generally requires a submicron pattern, prompting the use of an ArF excimer laser (193 nm) of a shorter wavelength than a conventional KrF excimer laser (248 nm) as a photolithography exposing light source. Thus, demand for a photosensitive polymer and a photoresist composition for a new chemically amplified photoresist suitable for the ArF excimer laser has increased.
In general, the chemically amplified photoresist composition for the ArF excimer laser needs the following requirements. The requirements of the chemically amplified photoresist composition are typically: (1) being transparent against 193 nm wavelength, (2) being thermally excellent (e.g., having a high glass transition temperature), (3) having excellent adhesion to a layer, (4) having high resistance to dry etching, (5) being capable of being easily developed using a developer (e.g., 2.38 wt % of tetramethyl ammonium hydroxide (TMAH)) which is very common in semiconductor manufacturing.
However, a common polymer for a chemically amplified photoresist for ArF excimer laser, e.g., terpolymer containing methylmethacrylate, t-butylmethacrylate and methacrylate monomers, does not satisfy all the above. In particular, the polymer has very weak resistance to etching and weak adhesion to a layer. Also, when using a developer which has been widely used for most other photoresist films, a non-exposed portion is also developed due to a plurality of hydrophilic functional groups being connected to the polymer, e.g., carboxyl group, so the critical dimension of a pattern tends to change. Thus, the developing should be performed using extra developer having a low concentration. However, if the concentration of the developer is very low, deviation in the critical dimension of the pattern markedly increases because the critical dimension of the pattern is very sensitive to changes in the concentration of the developer.
Thus, recently, research has been conducted into a photosensitive polymer suitable for use with an ArF excimer laser, in which an alicyclic compound such as isobornyl, adamantyl and tricyclodecanyl groups is introduced to a backbone of the polymer to improve resistance to etching. However, these polymers have defects too. For example, resistance to dry etching is still unfavorable, and adhesion to a layer is poor, thus causing lifting and/or instability of photoresist patterns.
The present invention is directed to overcoming or at least reducing the effects of one or more of the problems set forth above.